Light-Emitting Diode Package With Substantially In-Plane Light Emitting Surface and Fabrication Method
The present specification discloses a novel light emitting diode package having a package substrate with a light emitting layer bonded to the package substrate. Unlike conventional LED packages (such as those shown in FIGS. 1 and 2), the chip handling substrate typically located between the package substrate and the light emitting layer is not present. In addition, the LED package of the present specification may comprise an insulating layer formed on the package substrate and the light emitting layer. The LED package of the present specification may further comprise an interconnect metal formed on the insulating layer and the light emitting layer, wherein the interconnect metal electrically connects the light emitting layer to the package substrate.
The present specification is a novel LED package and a fabrication method for making such a package.
BACKGROUND OF THE INVENTIONA conventional LED package 100 typically requires the fabrication of the LED chip 140 by attaching an LED epitaxial wafer comprising the blue light emitting layer 140b to a LED chip handling substrate 140a, e.g., silicon. The next step comprises attaching the LED chip 140 onto the package substrate 110 using, for example, a die-attach material. Then, after the LED chip 140 is attached to the package substrate 110, a bond wire 160 is necessary to connect the LED bond pads (either p-pad or n-pad) 170a to an package bond pad 170b. The bond wire 160 and bond pads 170a and 170b are used to connect the LED chip to the package. As an example, in
For a conventional LED package 100, the distance, h, between the surface of the blue light emitting layer 140b to the surface of the metal layer 120 is a sum of their thicknesses. In the example of
As can be seen from the foregoing description, conventional LED packages and the fabrication processes for making them suffer from several disadvantages including, but not limited to, costs associated with the extra silicone required to form the base portion 130a of the silicone dome 130, and the extra steps and material associated with forming an LED die 140 including the LED chip handling substrate 140a and the bond wire 160.
There is therefore a long felt need for an LED package that overcomes these disadvantages and can be manufactured and packaged at reduced costs while maintaining the light emission performance of current LED devices.
BRIEF DESCRIPTION OF THE INVENTIONGenerally, the present specification discloses a novel LED package and a novel fabrication method for making such a package.
In one embodiment, the novel light emitting diode package may comprise a package substrate with a light emitting layer bonded to the package substrate. Unlike conventional LED packages (such as those shown in
In one embodiment, a novel fabrication method for making such a package is disclosed. This fabrication method may include the step of bonding a light emitting layer of an LED epitaxial wafer directly to a package substrate. The LED epitaxial wafer may also comprise a silicon substrate attached to the light emitting layer. The light emitting layer may then be exposed after having bonded the light emitting layer to the package substrate by removing the silicon substrate of the LED epitaxial wafer. Once the silicon substrate has been removed, the fabrication method may then utilize wafer level processing to form an insulating layer on both the package substrate and the exposed light emitting layer and then forming a metal interconnect layer on the insulating layer and the exposed light emitting layer.
The fabrication process, for example, takes advantage of wafer-level processing to reduce costs of fabricating the package.
A novel LED package structure and a fabrication method for making such a structure will now be described more fully with reference to the accompanying drawings. The drawings are not necessarily drawn to scale and certain features of the invention may be shown exaggerated in scale or in schematic form in the interest of clarity and conciseness.
In describing various embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology used in this specification. It is to be understood that each specific element includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.
Certain embodiments of the invention provide a novel LED package, and a fabrication method for making such a package, where an LED epitaxial wafer is directly bonded to an LED package substrate. Advantageously, the conventional intermediate step of forming a LED chip comprising the LED epitaxial wafer and a chip handling substrate is eliminated. The result is a novel LED package where the light emitting surface of an LED chip is substantially planar with the surface of the package substrate.
The insulation layer 350 is formed on the light emitting layer 340 and within the recess 320b of the metal layers 320. The recess 320b allows the insulation layer 350 to be in contact with the substrate 310 through the metal layer 320. As a result, package solder pads 320c and 320d are electrically isolated from each other. The metal interconnect layer 360 is formed on the insulation layer 350.
In contrast to conventional LED packages, the light emitting layer 340 is formed on metal layer 320 without an intermediary chip handling substrate such as elements 140a and 240a as discussed with regard to
Further in contrast to conventional LED packages, insulation layer 350 and metal interconnect layer 360 replaces a conventional fragile bond wire (e.g., 160 in
Region A includes the light emitting layer 340, the insulation layer 350, metal interconnect layer 360, bonding metal layer 320a, and substrate 310. The light emitting layer 340 may comprise an n-type gallium nitride (“n-GaN”) layer 340a and a p-type gallium nitride (“p-GaN”) layer 340b. The formation of package solder pads 320c and 320d may be interchangeable depending which piece is electrically connected to the n-GaN layer 340a and the p-GaN layer 340b. Package solder pad 320c is electrically connected to the n-GaN layer 340a and is therefore a cathode. Package solder pad 320d is electrically connected to the p-GaN layer 340b and is therefore an anode.
Also depicted in
Regarding the reflection layer 390a, it can be surrounded by the protection metal layer 390b. Reflection layer 390a may be formed of a reflective material such as silver and/or nickel. The reflection layer 390a is provided for reflecting light that is emitted by the light emitting layer 340 toward the surface of the substrate 310. Regarding the protection metal layer 390b, it protects the surface of reflection film 390a from being in contact with chemicals used in subsequent fabrication processes.
Dielectric layer 380 is also deposited on the LED package. The dielectric layer 380 passivates and insulates reflection film 390a and protection metal layer 390b from the bonding metal layer 320a. Isolation of the reflection 390a and protection metal layer 390b from the bonding metal layer 320a is necessary because the reflection film 390a and protection metal layer 390b are in contact with p-GaN layer 340b while the bonding metal layer 320a is in contact with n-GaN layer 340a.
The light emitting layer 340, the reflection layer 390a, and the protection metal layer 390b are bonded to substrate 310 via the bonding metal layer 320a. The light emitting layer 340 is further connected to the package solder pad 320c of the package 300 via the bonding metal layer 320a. Insulation layer 350 is formed on the light emitting layer 340 and the bonding metal layer 320a. The insulation layer 350 also is formed within recess 320b of the bonding metal layer 320a. Metal interconnect layer 360 is then formed on the insulation layer 350 and is connected to the package solder pad 320d of the package 300.
There are several benefits that result from the novel LED structures disclosed above. For example, there is a reduction in costs for both materials and the manufacturing process. With regard to materials, the silicone domes (e.g., 330 in
With regard to the manufacturing process, conventional steps that required die-level processing can be replaced with wafer-level processing steps. For example, with regard to
The LED package of the present specification also provides an improvement in the performance of the LED package in comparison to conventional LED packages. The elimination of a conventional chip handling substrate (e.g., e.g., 140a in
The novel LED packages described above are achieved by a novel fabrication method in which the semiconductor light emitting layers are directly transferred, via wafer bonding, onto the package surface without the conventional step of forming an LED chip having a chip handling substrate.
First, in
In
In
The step shown in
In
In
In
In
As a consequence of these process steps, the light emitting surface 510 is nearly in the same plane as the surface of the package metal surface 515b. The silicone dome 530 of the present specification does not require a base portion to maintain the light extraction efficiency of the LED device from an optical property point of view, since the chip handling substrate is no longer present. In comparison to a conventional package dome size (e.g., as depicted in
The fabrication methods described in
The remaining steps are similar to those described with respect to
As previously discussed, the addition of a phosphor layer 535 on top of the light emitting layer 510 changes the wavelength of light emitted by the light emitting layer 510. Due to the elimination of the LED chip handling substrate, the phosphor layer 535 is closer to the surface of the package as compared to conventional LED packages. With the elimination of the LED chip handling substrate, the silicone base of the silicone dome can be reduced in comparison to conventional bases for LED packages having phosphor. Therefore, the dome size for LED packages having a phosphor layer can also be smaller than conventional LED packages, while maintaining the light extraction efficiency.
Other objects, advantages and embodiments of the various aspects of the present specification will be apparent to those who are skilled in the field of the invention and are within the scope of the description and the accompanying Figures. For example, but without limitation, structural or functional elements might be rearranged consistent with the present specification. Similarly, principles according to the present specification could be applied to other examples, which, even if not specifically described here in detail, would nevertheless be within the scope of the present specification.
Claims
1. A light emitting diode package, comprising:
- a substrate;
- a bonding layer disposed on a surface of the substrate and having a first portion of the bonding layer electrically isolated from a second portion of the bonding layer;
- a first solder pad electrically connected to the first portion of the bonding layer;
- a second solder pad electrically connected to the second portion of the bonding layer;
- a light emitting layer having a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type that is different from the first conductivity type, the light emitting layer disposed on the first portion of the bonding layer;
- an insulating layer formed in a recess between the first portion of the bonding layer and the second portion of the bonding layer; and
- an interconnect layer formed on the insulating layer and the light emitting layer,
- wherein the interconnect layer electrically connects the second semiconductor layer and the second solder pad, and the first portion of the bonding layer electrically connects the first semiconductor layer and the first solder pad.
2. The light emitting diode package of claim 1, wherein the bonding layer comprises a metal layer and the light emitting layer is directly bonded to the metal layer on an upper surface of the substrate.
3. (canceled)
4. The light emitting diode package of claim 2, wherein the metal layer comprises the recess exposing a portion of the substrate, and a portion of the insulating layer is in contact with the exposed portion of the substrate.
5. (canceled)
6. (canceled)
7. The light emitting diode package of claim 1, wherein a thickness of the light emitting layer is equal to a distance from an upper surface of the bonding layer to an upper surface of the light emitting layer.
8. The light emitting diode package of claim 1, wherein the light emitting layer has a thickness of 5 micrometers and wherein a distance from a top surface of the metal layer and a top surface of the light emitting layer is 5 micrometers.
9. The light emitting diode package of claim 1, further comprising:
- a phosphor layer formed on the light emitting layer.
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
21. The light emitting diode package of claim 1, wherein each of the first solder pad and the second solder pad extend from a first surface of the substrate to a second surface of the substrate opposite of the first surface.
22. The light emitting diode package of claim 1, wherein the interconnect layer is disposed on a surface of the second portion of the bonding layer and an upper surface of the first solder pad.
23. The light emitting diode package of claim 1, wherein the interconnect layer is disposed on a surface of the second portion of the bonding layer.
24. The light emitting diode package of claim 21, wherein the interconnect layer is disposed on a surface of the second portion of the bonding layer and a surface of the second solder pad.
25. The light emitting diode package of claim 21, wherein the interconnect layer is disposed on a surface of the second portion of the bonding layer.
26. The light emitting diode package of claim 1, further comprising a dome formed over the light emitting layer and having curved upper surface extending from an upper portion of the first solder pad to an upper portion of the second solder pad.
27. The light emitting diode package of claim 1, wherein the light emitting layer is disposed on the first portion of the bonding layer but not the second portion of the bonding layer.
28. The light emitting diode package of claim 1, wherein the interconnect layer electrically connects the second semiconductor layer, the second bonding layer, and the second solder pad.
Type: Application
Filed: Mar 18, 2015
Publication Date: Sep 22, 2016
Inventors: Chih-Wei Chuang (Albany, CA), Chao-Kun Lin (San Jose, CA), Kai Liu (Dublin, CA)
Application Number: 14/661,379